Standards for the disposal of sewage have continually risen. Conversely, population pressure has continually called for the increased use of land. Thus, land which is marginal in regard to the treatment of sewage is receiving increased pressure for the ability to be put to its best use.
Septic tanks in various embodiments have been used for some 130 years to treat sewage when sewer systems are not available. This anaerobic process decomposes organic material utilizing enzymes and microbes which thrive in an environment devoid of oxygen. Untreated human waste and/or sewage from a building comprising both liquids and water carried solids, are discharged into septic tanks for partially effective decomposition and clarification by biological, physical and other natural processes. After the partial decomposition, the effluent is often discharged directed to the entry of a subsurface drain field for percolation into the subsoil under aerobic conditions. The discharge of effluent to a subsurface drain field at this point brings into focus the ability of the land to handle the burden.
To lessen the burden on the land and thereby increase the likelihood of approval for the use of the land, septic tank effluent has been treated secondarily before the discharge of the effluent to the subsoil.
In 1962, Lloyd Davis, in his U.S. Pat. No. 3,057,796 set forth a septic tank with a surrounding gravel bed. From the gravel bed, however, the effluent passes directly to the surrounding subsoil. In the present invention, an upflow filter is used which effectively collects the effluent so that the effluent can be passed to the final treatment phase.
In 1965, Frederick P. Willians in his U.S. Pat. No. 3,202,285 illustrated and described the further treatment of septic tank effluent in an adjacent aerobic tank. In 1974, Henry B. Carlson, in his U.S. Pat. No. 3,784,012, disclosed the construction of a septic tank positioned within the top of a structure forming a leaching pool wherein the septic tank effluent was further treated before reaching the surrounding subsoil.
In 1975 or earlier, John Hamilton of Seattle, Wash., first treated wastes discharged from an institution or family dwelling in a two compartment concrete septic tank. After passing through the two compartments the effluent is treated downstream in two concrete anaerobic upflow filters.
In 1976, Edward J. Jordan and John R. Snyder, in their U.S. Pat. No. 3,950,252, illustrated and described their overall upflow filter to be used with a home sewage treatment plant. They provided a concrete container having first and second upflow filtering chambers inclusive of gratings having filtering media.
In all of the above patents a separate system is necessarily constructed. This naturally expands the expense of the system, and subjects the system to added potential for breakdown.
It is believed that a continuing review of patents and literature will not reveal a method, configuration or equipment for the treatment of sewage whereby anaerobic digestion and filtering processes are undertaken as disclosed in the present invention. The advantages of the present invention are discussed in the Summary of the Invention.